Vapor effects of persistent gas munitions are examined during various U.S. chemical warfare tests in San Jose Island, Panama.

Tests of persistent gas munitions during U.S. chemical warfare tests on San Jose Island, Panama during World War II. Chemical warfare tests shows U.S. troops firing 4.2 inch mortars and 105mm howitzers laying down a mustard gas barrage. Smoke rises from shell fire in the jungle. A technician examines a bombed area in the jungle. Vapor effects of persistent gas munitions are examined. Bodies of captured Japanese soldiers who were in the bombardment area are examined within three hours of the bombardment. U.S. troops without any protective clothing advance through the jungle area 48 hours after the bombardment. The troops fire mortars and howitzers.